i drive a 2004 wrx, a few weeks ago i installed a vf39 pinks large tmic with an xpt tuning vf39 ots map. car has been running fine the last few weeks. last night i put in a walbro 255lph pump in, didnt boost at all on my way home. on my way to work this morning i was passing a car in 4th gear at wot, just after i hit peak boost my car sounded and felt like it was sputtering or missing, i let off the gas and my cel flashed a few times and went away. so i proceeded to hit peak boost again just to see if it was a fluke. same thing, only this time my cel stayed on afterwords. when i got home i put learning view on it and it came back with 2 codes p0301 and p0302 (cylinder 1 misfire and cylinder 2 misfire)
would this have anything to do with the pump i just put in? because it ran fine through the gears at wot before.
i couldnt see/hear any air leaks under the hood, and my vac at idle is around 20 and pretty steady.
I wouldnt think the pump was the culprit. Have you driven the car at wot after the vf39 map and before you put a new pump in with no issues? And it doesnt misfire any other time? Are you able to view fuel trim with your scanner?
Interesting. well if it were me, the first thing i would do is put the oem pump back in. I havent upgraded my fuel pump yet so i cant say whether or not one may cause problems. If for some reason this pump was causing too much fuel delivery ( even though thats controlled by a pressure regulator and injector pulse width) the ecu will cut back on injector pulse so you will see negative fuel trim on a scanner and also sometimes, the ecu will make coils fire a larger spark to compensate for too much fuel which will over time easily burn a coil out. Easiest thing to do would be to find someone with a good scanner so you can determine WHY its misfiring. But if you throw oem pump back and its still missing i would suspect bad coils. Bad injector are also possible too but given what you said i would think coils first.
Also, have you upgraded your injectors? May have to with that turbo and ots map if you havent.
If not i would also test injector resistance just to make sure theyre working correctly, ya know?
should be like 12 ohms or so, i think.
I wouldnt think so due to the fact that the fuel pump doesnt determine how much fuel is going into the cylinder. You said it was running fine after the turbo upgrade and re-map. Your new map and injectors are what determines how much fuel is coming through. Fuel pressure will always be consistent via your fuel pressure regulator. A fuel pump upgrade just makes sure the fuel is getting there fast enough.
hmmm thats wierd, so it almost has to be to do with the pump...hopefully ill get some time to pull it out tonight or tomorrow night and see whats going on with it....
got another thought.
when i got the pump it came with another one of those square fuel strainer lookin things, but it was smaller than the stock one, so i used the stock one, but it ddnt seem to press on the pump as tight as factory, maybe it leaks a little at full boost. does the size of the strainer matter? should i maybe try the one that came with the new pump?
well i found the problem......long story, but here it is...
got off work today and immidiately put my car in the garage, took out the pump, put on the correct sock that came with it, made sure clamps were all tight on the fuel lines. took it for a drive, no change.....put it back in the garage, changed the fuel filter, and took out all the plugs, the diodes were worn down a bit (ngk v power plugs), 1 and 2 hardly had the v in them at all(even though i just changed them less than a year ago) the gaps were way off on all of them, cylinders 1 and 2 (the ones that misfired) were gaped at like .40-.45 and 3 and 4 were gapped at like 35. i must not have checked the gaps when i put them in last time......so i put new plugs in anyway, and made sure gaps were correct, took it out for another drive.........same thing, misfiring after 4000 rpm, but then as soon as i hit 4000 rpm its like i hit a brick wall, the car actually slowed down it was bogging so bad.........put it back in the garage, put in the oem fuel pump and sock and took it for a drive again......same thing.......put it back in the garage, opened the hood and stared at it for like 20 mins(not happy at this point lol)....so i was looking at the intercooler pipe from the throttle body to the intercooler, it is the one that came with the car, because when i ordered all the parts, that hose never came(still havent got it btw) i poked it with my finger and it wiggled, so i checked the clamp, and is was loose, the hose was actually off of the intercooler a little bit on the bottom. so i pulled off the intercooler to make sure the bolts and clamps were all tight under it, bolts and clamps were all loose, tightened them all up, went to advance and got a new hose(the one on there was really soft cracked a bit, put the intercooler back on and tightened everything back up and took it for a ride.......SUCCESS..car runs great now, no cel, no misfire..........musta been just coinsidence that this happened rite after i put in the new pump, given it was a week after the injector/turbo/intercooler install, i suppolse everything lossened up with the heat and vibration, idk why i didnt think about that befor....but now i have the oem pump back in, but it will stay there for a few days i think
sory for the book of a post, but thanks for your advice, and tryin to help me figure all this out.
I hate when that happens. I figured the new pump wasnt the culprit but it makes you think it is when a new problem occurs at the exact same time you switch out a part, I know the feeling. Well glad to hear its back and healthy again!
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